The invention relates to turbine engine blades made of composite material comprising fiber reinforcement densified by a matrix.
The intended field is that of gas turbine blades for aeroengines or industrial turbines.
Proposals have already been made to fabricate composite material blades for turbine engines. Reference may be made in particular to patent applications FR 2 939 129 and FR 2 939 130 filed jointly by Snecma and Snecma Propulsion Solide. Those applications describe in particular fabricating a turbine engine blade out of composite material comprising fiber reinforcement densified by a matrix. More precisely, the method described in those two documents and applied to fabricating a blade presents the special feature of a fiber blank that is made by three-dimensional weaving and that is shaped in order to obtain a single-piece fiber preform with a first portion forming a preform for a blade root and an airfoil, and at least one second portion forming a preform for an inner or an outer platform of the blade. Thus, once the preform has been densified, it is possible to obtain a composite material blade having fiber reinforcement constituted by the preform and densified by the matrix, and forming a single piece that has an inner or an outer platform incorporated therein.
The blade obtained by such a method presents the drawback that its outer platform cannot incorporate both a function of providing sealing with the casing that surrounds the blades (by having wipers present) and an aerodynamic function (by having overhangs present that define the outside of the flow passage for the gas stream through the turbine). Furthermore, at its root, the overhangs of the inner blade platform that is obtained by that method can break under the effect of the high levels of force to which they are subjected in operation (this force being due to the centrifugal force of rotation).